Communication between the home screen and WRT

Communication between the home screen and WRT happens at the system level, and is therefore automatic. When WRT receives this communication, it fires events. The widget must respond to these events by calling a "decide" function that determines in which view (home screen or full screen) to display the widget. For instructions on implementing and calling this function, see Determining whether to display home screen or full screen.

User action	System level	Widget must
Sends the home screen to the foreground by turning the device on, selecting home screen from the open applications list, exiting full screen widget, and so forth.	Starts JavaScript timers for all widgets added to the home screen. Sends `onshow()` and `onresize()` events for all widgets added to the home screens.	Call a "decide" function in reponse to `onshow()` and `onresize()`. For information, see Determining whether to display home screen or full screen.
Adds a widget to the home screen	Launches the widget in the background. Fires `onload()` and `onshow()` events. May prompt user for permissions. Sends a bitmap update of the widget data to the home screen.	Call a "decide" function in response to `onload()` and `onshow()`. For information, see Determining whether to display home screen or full screen.
Removes widget from the home screen	Shuts the widget down.	None needed.
Sends the home screen to the background by selecting another application from the open applications list, opening a home screen widget in full view, and so forth.	Suspends timers. Suspends bitmap updates of the widget. Fires an `onhide()` event.	None needed.
Opens the home screen widget in full screen view	Suspends all other home screen widgets. Starts the JavaScript timers for the selected widget. Fires `onshow()` and `onresize()` events for the selected widget.	Call a "decide" function in response to `onload()` and `onresize()`. For information, see Determining whether to display home screen or full screen.